RESERVOIR SILTATION AND SEDIMENT YIELD IN THE KRUGER NATIONAL PARK, SOUTH AFRICA: A FIRST ASSESSMENT

Human-induced soil erosion is a widespread phenomenon in South Africa, and soil erosion rates reported are among the highest in the world. In addition to human disturbance, unfavourable environmental conditions are mentioned to explain the situation. But data on natural erosion from undisturbed sites are rare. This paper presents the first assessment of sediment yield as an integrate measure of erosion, deposition and sediment transport from five catchments located entirely within Kruger National Park (KNP). KNP has been spared from agricultural development for a century and represents a near to natural geo-ecosystem in the semi-arid savanna biome. Sediment yield estimates are based on a survey of post-dam deposits in five reservoirs located in the south-eastern part of KNP. Reservoir lifetime ranges from 40 to 60?years and the size of the catchments from 8 to 100?km2. The results show distinct relations of long-term average sediment yield (SY) and area-specific sediment yield (SSY) with catchment size. Despite the unfavourable semi-arid environmental conditions, SY is comparatively low. SY varies from 130?+/-?45?t?y-1 for the 8?km2 catchment to 1130?+/-?230?t?y-1 for the 100?km2 catchment. SSY is 55?+/-?15?t?km-2?y-1 for catchments of 12?+/-?3?km2 and 11?+/-?2.4?t?km-2?y-1 for the 100?km2 catchment. The latter finding suggests that decrease of SSY with increasing catchment size is not attributable to human disturbance only. However, further research is necessary to improve and enlarge the database and to verify first results and hypothetical conclusions. Copyright (c) 2012 John Wiley & Sons, Ltd.